Orthodontic brackets represent a principal component of all corrective orthodontic treatments devoted to improving a patient's occlusion. In conventional orthodontic treatments, an orthodontist affixes brackets to the patient's teeth and engages an archwire into a slot of each bracket. The archwire applies corrective forces that coerce the teeth to move into correct orthodontic orientation. Traditional ligatures, such as small elastomeric O-rings or fine metal wires, are employed to retain the archwire within each bracket slot. Due to difficulties encountered in applying an individual ligature to each bracket, self-ligating orthodontic brackets have been developed that eliminate the need for ligatures by relying on a movable portion or member, such as a latch or slide, for retaining the archwire within the bracket archwire slot. As such, self-ligating orthodontic brackets require manipulation of the movable portion between an opened position, in which the archwire slot is exposed so as to allow the clinician to remove an archwire from the archwire slot and then insert a new archwire into the archwire slot, and a closed position, in which the movable member retains the archwire in the archwire slot to effectuate treatment.
While such self-ligating brackets are generally successful in achieving their intended purpose, there remain some drawbacks. Manipulation of the movable member requires mechanical actuation of the movable member. In this regard, one drawback is that manipulation often requires use of a tool. The clinician may insert a tool, such as a scalar, into direct contact with the orthodontic bracket and apply a direct mechanical force to the movable member to move it from a closed position to an opened position. Not only is a tool often required, depending on the design of self-ligating orthodontic bracket, the tool may be custom made for that particular bracket design. By requiring a custom tool to be used, treatment may become more complex simply because the clinician must keep track of yet another tool to provide proper treatment.
Another drawback is that orthodontic brackets are generally very small mechanical devices. Due to their small size, manipulation of the movable member often requires excellent visual acuity, manual dexterity, and hand-eye coordination. The lack of any single one of these attributes is particularly problematic when a tool is required to manipulate the movable member, because the tool usually must be inserted into a tiny receptacle to unlatch the movable member and to move it to the opened position. In addition, depending on the orthodontic bracket design, opening the movable member may require specialized training, and the clinician's efficiency at manipulating the movable member may be gained only with significant experience with that particular orthodontic bracket. In any case, chair time for the patient may initially be longer until the clinician gains sufficient experience at manipulating the movable member.
Even though successful, in view of the above, utilizing self-ligating orthodontic brackets may require significant initial chair time, specialized equipment, and clinical training, all of which increases treatment costs. Thus, when present, these characteristics act as barriers to widespread adoption and acceptance of new self-ligating orthodontic bracket designs.
There are also other problems associated with self-ligating brackets. For instance, manufacturing self-ligating orthodontic brackets typically requires subsequent assembly of each of the separately manufactured components. Due to their small size, assembling the movable member together with the bracket body may require special tooling, highly trained workers, or both, all of which drives up manufacturing costs.
Self-ligating orthodontic brackets may also exhibit performance issues that are related to the manufacturing tolerances of each of the movable member and the bracket body. The manufacturing tolerances may become problematic when the separately manufactured components are assembled. Following assembly, when the movable member is closed, the bracket body and the movable member collectively form a closed lumen for capturing the archwire. A close fit between the closed lumen and the archwire is believed to be important for achieving excellent rotational control during orthodontic treatment. Yet, to allow the movable member to be assembled with and move relative to the bracket body between the opened and closed positions, there must be some clearance in the manufacturing tolerances between the bracket body and the movable member by design. When the movable member and the bracket body are assembled, these manufacturing tolerances “stack up” to provide a lumen which may vary significantly in its labial-lingual dimension between different brackets made to the same tolerance specification. Therefore, some of the brackets may provide a relatively loose fit while other brackets may provide a relatively tight fit with the same archwire. Variation in the fit of the archwire with different brackets is believed to result in a diminished capacity to control the rotation of some teeth, such as near the finishing stages of orthodontic treatment. While there may be several factors that cause a reduction in rotational control, it is believed that one of the major causes is the loose fit of the archwire within the archwire slot of the bracket when the movable member is closed.
Thus, while self-ligating brackets have been generally successful, manufacturers of such brackets continually strive to improve orthodontic bracket use and functionality. In this regard, there remains a need for self-ligating orthodontic brackets that reduce chair time and/or improved rotational control during orthodontic treatment, such as during the finishing stages thereof.